After I have updated kernel to 2.6.18-274.12.1.el5 and reboot server the network is not up. From console I saw lines something like during the system is booting:ADDRCONF(NETDEV_UP): bond1: device doesn't existADDRCONF(NETDEV_UP): bond1: link is not ready

OK, then try to stop the network, check the module is still loaded and up your network manually with ip and ifenslave. I would say it would look like this

thanks, I will try

What have you got about network in your syslog ?

That what I have found in the /var/log/messages is very interesting.As I told above, in my box I have 4 nic, eth0/eth1 is internal Intel Pro 1000 (e1000e) and eth2/eth3 is external Intel Gigabit ET Dual Port E1G42ETBLK (igb)

On CentOS 6 there is a file /etc/udev/rules.d/70-persistent-net.rules that has udev rules in it to handle this sort of thing. I am not sure if the same rules will work on CentOS 5 but it could be worth a try as long as you have local access to the machine to revert the change in case it breaks it completely!